The objective of the proposed research is to compare the effectiveness of estrogen and aromatizable and non-aromatizable androgens in the organization and activation of pup-killing behavior in male mice. The above question is examined in two experiments. In the first experiment, the organization of pup-killing behavior is studied in male mice castrated neonatally, treated at the same time with a single injection of oil, estradiol, testosterone, androstenendione, androstanedione, or dihydrotestosterone, and injected in adulthood with testosterone. In the second experiment, the activation of pup-killing is examined in male mice castrated in adulthood and treated with oil or one of the above steroids. The results should substantially contribute to our knowledge of the role of hormone metabolites in modulating testosterone-dependent masculine behaviors. They ultimately may be important for our understanding of human deviant behaviors such as child abuse.